Influence of dead layer on the response function of planar and coaxial Ge detector using Monte Carlo method

Abstract

Germanium crystals have a dead layer that causes a decrease in efficiency since the layer is not useful for detection but strongly attenuates photons. The thickness of this inactive layer is not well known due to the existence of a transition zone where photons are increasingly absorbed. Therefore, using data provided by manufacturers in the detector simulation model, some strong discrepancies appear by changing the dead layer. Investigations into the Ge detector response functions for gamma rays have been conducted using straightforward physical mechanisms implemented by Monte Carlo simulations. The detector response function feature's most probable interaction mechanisms are described. The Monte Carlo method is applied to simulate the calibration of a HPGe detector in order to determine the total inactive germanium layer thickness and the active volume that is needed in order to study the response function for both types of detectors. Results indicated a strong impact of dead layer variations on the response function of the simulated detectors.